From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A103AECE561 for ; Mon, 24 Sep 2018 11:41:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6610121486 for ; Mon, 24 Sep 2018 11:41:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6610121486 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729605AbeIXRnT (ORCPT ); Mon, 24 Sep 2018 13:43:19 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:51034 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728911AbeIXRnS (ORCPT ); Mon, 24 Sep 2018 13:43:18 -0400 Received: from localhost (ip-213-127-77-73.ip.prioritytelecom.net [213.127.77.73]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id 98D331072; Mon, 24 Sep 2018 11:41:38 +0000 (UTC) From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Aaron Knister , Ira Weiny , Jason Gunthorpe Subject: [PATCH 3.18 082/105] IB/ipoib: Avoid a race condition between start_xmit and cm_rep_handler Date: Mon, 24 Sep 2018 13:34:08 +0200 Message-Id: <20180924113121.256237299@linuxfoundation.org> X-Mailer: git-send-email 2.19.0 In-Reply-To: <20180924113113.268650190@linuxfoundation.org> References: <20180924113113.268650190@linuxfoundation.org> User-Agent: quilt/0.65 X-stable: review MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Aaron Knister commit 816e846c2eb9129a3e0afa5f920c8bbc71efecaa upstream. Inside of start_xmit() the call to check if the connection is up and the queueing of the packets for later transmission is not atomic which leaves a window where cm_rep_handler can run, set the connection up, dequeue pending packets and leave the subsequently queued packets by start_xmit() sitting on neigh->queue until they're dropped when the connection is torn down. This only applies to connected mode. These dropped packets can really upset TCP, for example, and cause multi-minute delays in transmission for open connections. Here's the code in start_xmit where we check to see if the connection is up: if (ipoib_cm_get(neigh)) { if (ipoib_cm_up(neigh)) { ipoib_cm_send(dev, skb, ipoib_cm_get(neigh)); goto unref; } } The race occurs if cm_rep_handler execution occurs after the above connection check (specifically if it gets to the point where it acquires priv->lock to dequeue pending skb's) but before the below code snippet in start_xmit where packets are queued. if (skb_queue_len(&neigh->queue) < IPOIB_MAX_PATH_REC_QUEUE) { push_pseudo_header(skb, phdr->hwaddr); spin_lock_irqsave(&priv->lock, flags); __skb_queue_tail(&neigh->queue, skb); spin_unlock_irqrestore(&priv->lock, flags); } else { ++dev->stats.tx_dropped; dev_kfree_skb_any(skb); } The patch acquires the netif tx lock in cm_rep_handler for the section where it sets the connection up and dequeues and retransmits deferred skb's. Fixes: 839fcaba355a ("IPoIB: Connected mode experimental support") Cc: stable@vger.kernel.org Signed-off-by: Aaron Knister Tested-by: Ira Weiny Reviewed-by: Ira Weiny Signed-off-by: Jason Gunthorpe Signed-off-by: Greg Kroah-Hartman --- drivers/infiniband/ulp/ipoib/ipoib_cm.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c +++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c @@ -997,12 +997,14 @@ static int ipoib_cm_rep_handler(struct i skb_queue_head_init(&skqueue); + netif_tx_lock_bh(p->dev); spin_lock_irq(&priv->lock); set_bit(IPOIB_FLAG_OPER_UP, &p->flags); if (p->neigh) while ((skb = __skb_dequeue(&p->neigh->queue))) __skb_queue_tail(&skqueue, skb); spin_unlock_irq(&priv->lock); + netif_tx_unlock_bh(p->dev); while ((skb = __skb_dequeue(&skqueue))) { skb->dev = p->dev;